Revert "When monitoring idle connections, only call eof on tcp socket (#912)" (#914)

This reverts commit 976fab5.

Author: quinnj

src/ConnectionPool.jl

@@ -261,8 +261,8 @@ TODO: or if response data arrives when no request was sent (isreadable == false)
 """
 function monitor_idle_connection(c::Connection)
     try
-        if eof(tcpsocket(c.io))                                  ;@debugv 3 "💀  Closed:     $c"
-            isopen(c.io) && close(c.io)
+        if eof(c.io)                                  ;@debugv 3 "💀  Closed:     $c"
+            close(c.io)
         end
     catch ex
         @try Base.IOError close(c.io)